GB2270394A

GB2270394A - Fault detection in an engine control system

Info

Publication number: GB2270394A
Application number: GB9318251A
Authority: GB
Inventors: Dieter Sorg; Martin Streib
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1992-09-05
Filing date: 1993-09-03
Publication date: 1994-03-09
Anticipated expiration: 2013-09-03
Also published as: DE4229774A1; JP3665351B2; GB2270394B; JPH06167237A; DE4229774C2; GB9318251D0; US5370094A

Abstract

Control means for an internal combustion engine comprises a measuring element 32 for detecting the setting of a throttle flap 14 of the engine, a measuring element 16 for detecting engine load independent of the measurement of the throttle flap setting, and a control unit 18 which compares measured values respectively indicative of the flap setting and engine load. If the difference value resulting from the comparison exceeds a predetermined threshold value, the throttle flap sensor 14 is determined to be defective and emergency operation of the engine can be initiated. Further measurement signals can he included in the comparison undertaken by the control unit 18 so as to recognise whether the value indicative of engine load is defective. The control means is particularly suitable for fault monitoring in conjunction with an electronically controlled throttle system. <IMAGE>

Description

2270394 FAULT DETECTION IN AN ENGINE CONTROL SYSTEM The present invention

relates to control means for an internal combustion engine of a vehicle and has particular reference to fault recognition in the context of engine control.

In modern control systems for internal combustion engines, 5 measuring devices for the detection of operating parameter magnitudes of an engine or of a vehicle in which the engine is installed are often used, the output signals of which devices form the basis for the engine control. Since undesired operating states of the engine could re-,tjlt. from faulty functions in the region of these measuring devices, these should be monitored for functional integrity. Particular significance attaches to monitoring of electronic output control systems (electronic accelerator pedal systems), in which the engine power and thus the vehicle speed are controlled on the basis of measurement signals from setting transmitters for an operating element actuated by the driver and, optionally also, for an outputsetting element. In the past, different measures have been proposed for the monitoring of such setting transmitters. For example, in the not prior- published German patent application DE-P 41 33 571.6 it is proposed, in conjunction with an output-setting element, to provide three setting transmitters, the measurement signals of which are checked one against the other for plausibility. In the event of a fault with one of the transmitters, the control of the engine takes place in the sense of a two-out-of -three selection on the basis of the two transmitters that have retained functional integrity. A procedure of that kind, however, would be less satisfactory in terms of complication in certain areas of application.

There is thus a need for control means in which the monitoring of a values detection system in an internal combustion engine can be effected in simple manner, preferably in association with preparation of a suitable procedure for emergency operation of the engine.

According to a first aspect of the invention there is provided control means for an internal combustion engine, comprising electrically actuable setting means for the setting of a settable device in dependence on the setting of an operating element actuable by the driver, at least one measuring member for detection of the setting of the device, at least one measuring member for detection.of a magnitude which represents a measure of the load of the engine and is not directly related to the setting of the device, and means for carrying out a plausibility check on the basis of these two magnitudes, a fault in the region of the measuring member detecting the setting being recognised when the two magnitudes differ impermissibly from each other.

According to a second aspect of the invention there is provided control means for an internal combustion engine, comprising measuring members for the preparation of at least two setting information values in respect of the setting of a settable device, at least one measuring member for the detection of a magnit ude which represents a measure of the load of the engine and is not directly related to the setting of the device, means for the performance of a control function at least on the basis of one of the setting information values, and means for fault recognition, wherein the at least two setting information values and the detected magnitude representing a measure of the engine load are checked with each other for plausibility and a fault is recognised at least when one of the magnitudes differs impermissibly from the others.

3 In the case of the latter aspect, two signal values as a rule remain free from faults, and the control of the engine can be undertaken on the basis of those signals.

In a case where a fault is recognised as present or no reliable setting information is available, an emergency running of an electronic power control system of the engine can be instituted in such a manner that the wish of the driver represents a target value for a magnitude representing a measure of the engine 1 oad independently of the setting information data, and the signal value representing this magnitude can be set to the target value in the sense of a regulation.

It is known from the Abstract of JP-OS 61/58 945 that, on the basis of a measurement signal of an air meter and a measurement signal for the throttle flap setting of an internal combustion engine, abnormalities of the air meter can be deduced and emergency running measures in the case of a fault can be undertaking.

Control means embodying the invention enables fault monitoring on the basis of at least one setting information value, a two-out-ofthree selection on the basis of two setting information values being particularly advantageous. In that case, a third setting transmitter is saved and, in the case of a fault, the control of the engine can be continued on the basis of the other two values. Through the saving of a third setting transmitter or with the use of merely one setting transmitter or one setting information value, operational reliability can be ensured and engine availability made certain with simultaneous reduction in complication. In particular, the control means offers the possibility to undertake emergency running still with substantial scope of function of an electronic engine control, system.

Particular advantages result from the use of a stepping motor, in which setting information is present through counting of the issued steps, so that merely one position sensor need be provided for safety monitoring or for regulation in conjunction with the engine power setting element.

Through the two-out-of-three selection in case of lack of Plausibility between compared signals, an emergency travel operation without restriction of function can be performed. In the case of an implausible stepping counter state, this can be synchronised on the basis of two other values.

The use of a signal value which is normally provided in an engine control system and derived from a load-detecting element independently of the setting data, for example from an air quantity meter, air mass meter or induction duct pressure sensor, or which is the basic injection signal (load signal) itself, is particularly advantageous.

Embodiments of the present invention will now be more particularly described with reference to the accompanying drawings, in which:

Fig. 1 is a schematic block diagram of an engine control system in which control means embodying the invention can be incorporated; Fig. 2 is a flow diagram, illustrating monitoring of a single setting transmitter by plausibility comparison in control means embodying the invention; Fig. 3 is a flow diagram illustrating monitoring of at least two setting transmitters by plausibility comparison with each other and with a load value in further control means embodying the invention; and Fig. 4 is a flow diagram illustrating performance of an emergency running operation of an electronic control system following fault detection by control means embodying the invention.

Referring now to the drawings there is shown in Fig. 1 a vehicle engine 10 which has an air induction system 12 in which a throttle flap 14 and a measuring element 16 for load detection are mounted.

Associated with the engine is control means comprising a control unit 18 which, in a first embodiment, supplies a signal by way of a first output line 20 to actuate an electrical setting motor 22, which is connected with the throttle flap 14 by way of a mechanical connection 24. In a second embodiment, further output lines 26 and 28 are provided, which are illustrated in dashed lines in Fig. 1 and control fuel metering and ignition instant setting.

A first input line 30 connects the control unit 18 with the measuring element 16 for load detection. Moreover, a measuring element 32 is provided, which is arranged at the flap 14 or the mechanical connection 24 to detect the setting of the flap and which is connected to a second input line 34 of the control unit 18. In 6 - the mentioned second embodiment, the measuring element 22 is a double setting transmitter, which generates two signal values representing the setting of the throttle flap 14. In that case a further input line 36 of the control unit 18, as illustrated in dashed lines in Fig. 1, connects the latter with the measuring element 32. A] so provided are input lines 38 to 40, which connect the control unit 18 with measuring elements 42 to 44 for detection of further operating parameter magnitudes of the engine 10 or of the vehicle.

In the system shown in Fig. 1, the engine control system 10 electronically controls at least fuel injection and throttle fl-ap setting. A basic injection signal (load signal) is formed in dependence on the magnitude representing engine load, which is detected by the measuring element 16, and on engine speed which is detected by one. of the measuring elements 42 to 44. On the basis of the injection signal, which is subject to different corrections referred to exhaust gas composition, height above sea level and so forth, the quantity of fuel to be supplied is determined and at least one injection valve is actuated. In addition, a target value for the setting of the throttle flap 14 is ascertained in dependence.on the setting of an operating element which is actuable by the driver and is detected by one of the measuring elements 42 to 44. Further operating magnitudes, such as engine temperature, battery voltage, engine speed, travel speed, traction control signals and so forth, can also be formed and play a part in, in particular, operational states outside actual travel operation, such as idling, starting traction control and so forth. A drive signal delivered by way of 7 the output line 20 is formed in the control unit 18 on the basis of this target value and optionally also subject to consideration of one of the measurement signals representing the setting of the throttle f 1 ap. The throttle flap 14 is in that case actuated in the sense of 5 an adjustment of the preset target setting.

The setting motor 22 can be a direct current motor, preferably a stepping motor. A first setting information value in respect of the throttle flap setting is provided by way of a step counter, which detects the delivered steps and can take the place of the measuring el ement 32. Alternatively, the measuring element 32 is present and comprises a single setting transmitter for the preparation of a second setting information value.

The measuring element 16 can be, for example, an air quantity meter, an air mass meter or an induction duct pressure sensor.

Control means embodying the invention can also be applied in advantageous manner to engine control systems without electrical actuation of the throttle flap. In systems of that kind, the throttle flap setting serves for idling recognition, for load detection in part ranges or for detection of an acceleration command of the driver for initiation of acceleration enrichment.

The operation of such control means, for checking of the setting detection of the throttle flap, is described in the following with reference to Figs. 2 to 4.

In Fig. 2, monitoring of the measuring element 32 concerns the first embodiment, in which merely one setting information value is provided by the measuring element. In the case of a stepping motor, the stepping counter is understood to represent the measuring element. The procedure illustrated in Fig. 2 is initiated only when the measuring element 16 operates correctly. The functional checking of the measuring element 16 can in that case be carried out in known manner.

After the start of the program part illustrated in Fig. 2, the measurement value DK of the measuring element 32, the rotational engine speed n, and the measurement value load of the load-measuring element 16 (air quantity Q L5 induction duct pressure P, air mass M L or the basic injection quantity t i formed on the basis of the quotient of air quantity or air mass and rotational speed) is detected in a first step.100. In the following description, the air mass is taken as the magnitude representing engine load.

In a following step 102, a target value for the inducted air mass, i.e. load, is ascertained from a characteristic values field on the basis of the measurement value DK of the measuring element 32 and the rotational speed n and, in a interrogation step 104 following thereon, the difference between this ascertained target value and the actual value of the air mass flow, i.e. load which is detected by the measuring element 16, is checked for a preset tolerance range. If this difference is smaller than a predetermined value A, then normal operation, i.e. fault-free operation of the measuring element 32 is recognised in a step 106, whereas if the difference exceeds the value A a fault state of the measuring element 32 is recognised in a step 108 and an emergency running procedure is initiated. After the steps 106 and 108, the program part is concluded and repeated at preset times.

If a stepping motor is used as drive, an emergency travel operation can even be avoided when the load-detecting element is operating correctly by new synchronisation of the stepping counter in tle flap is the case of implausibility. For this purpose, the throt moved to a defined point in the step 108, for example an end setting or another distinct point of the setting range (for example the torque reversal point of the setter), and the stepping counter is set to the associated value. The monitoring by means of the load measurement magnitude in that case serves for the fulfilment of Rafety requirements.

In another example, a comparison of setting measurement values can be performed in place of comparison of air mass values. In that case, a target setting value for the throttle flap is ascertained on the basis of the detected air mass flow value and the engine speed and the difference between this 'target value and the actual value detected by the measuring element 32 is tested for a preset tolerance range.

An example of an emergency running procedure, initiated by the control means in step 108, is illustrated in Fig. 4 for an engine control system with electrical actuation of the throttle flap.

After start of the program part illustrated in Fig. 4, the accelerator drive pedal settingJ3 and the measurement value detected by the measuring element 16, as well as other operating magnitudes such as travel speed, engine speed, battery voltage, traction control signals and so forth, are entered in a first step 200. In a following step 202, a target air mass flow value, i.e. target load, is ascertained from a characteristic values field in dependence on the accelerator pedal setting and, optionally also, on further operating magnitudes. In a step 204, the difference.& between the ascertained target value and the actual value detected by the measuring element 16 is formed and an output signal based on the regulating difference A is ascertained in a step 206, for example by a preset regulator equation with, for example, PID behaviour. In a step 208, the computed output signal value is delivered by way of the line 20 to the setting motor 22.

The described emergency running procedure accordingly involVes regulation of the air mass flow value influenced by the throttle flap 14 in place of the control or regulation of the position of the throttle flap 14 undertaken in the case of correct function of the measuring element 32. In other advantageous examples, the emergency running procedure is performed by the described regulating circuit in dependence on the other load values, such as air quantity or induction duct pressure, or on the load signal itself.

Fig. 3 shows the monitoring of the measuring element 32 for the second embodiment in which two setting information values in respect of the throttle flap 14 are present. These values originate from two setting transmitters, as illustrated in Fig. 1, or from one setting transmitter and from a stepping counter counting the steps of a stepping motor drive.

In a first step 300, the magnitudes evaluated for the subsequent checking are entered, namely a first setting value DK1 from the measuring element 32, a second setting value W2 also from the measuring element 32 or from a stepping counter, engine speed n and the engine load value detected by the measuring element 16.

In a following interrogation step 302 it is checked whether the measuring element is operating correctly. If this is not the case, an emergency running is initiated according to a step 304 and the program part is terminated. A monitoring of th e measuring element 32 5 does not take place in this case.

If, however, the measuring element 16 is functionally capable, the difference between the setting values W1 and DK2 is checked for a preset tolerance range in a first interrogation step 306. If the difference between these two values is smaller than a predetermined threshold vallie A, the measuring element 32 is evaluated as functionally capable in a step 309. If the amount of this difference exceeds the value A according to step 306, a first target value for the load is determined in a step 308 by reference to a characteristic values field in dependence on the first setting value W1 and the engine speed n as well as a second target value for the load by reference to a second characteristic values field in dependence on the second setting value W2 and the engine speed n.

In a step 310 following thereon, the difference between the first target load value and the actual load value ascertained by the measuring element 16 is ascertained. If this difference falls below a predetermined value B, the setting value DK2 is recognised as faulty according to a step 312. If the difference exceeds the threshold value B, the difference between the second target load value and the detected actual 1 oad value is formed in an interrogation step 314. If the amount of this difference exceeds a predetermined threshold value C, the setting value DK1 is recognised as faulty in a step 316. In the opposite case, a defect in the sense of no reliable setting information being present is recognised in a step 318.

After the steps 309, 312, 316 and 318, it is checked in an interrogation step 320 whether the afore-described monitoring had the consequence of recognition of the normal state, i.e. the recognition of the step 309. If this is the case, the control of the throttle flap is undertaken on the basis of the first and/or the second setting value according to a step 322 and the program part is terminated thereafter. If the result of the preceding monitoring was not the normal state recognised in step 309, it is checked in an interrogation step 324 following the step 320 whether the result was that of step 316, i.e. a faulty first setting value. If this is so, the control of the throttle flap is undertaken on the basis of the second setting value in a step 326. In the opposite case, it is checked in an interrogation step 328 whether the result was that of step 312, i.e. a faulty second setting value. If sP, the control of the throttle flap is undertaken on the basis of the first setting value in a step 330. If the second information value is derived from a stepping counter, this is set to the value preset by the first setting value and the control of the throttle flap is performed as in the normal state in a step 322. If the result of the interrogation step 328 was in the negative, no reliable setting information is present (the result of step 318) and the emergency running procedure, described by reference to Fig. 4, of regulation of the throttle flap on the basis of a target load value and an actual load value is undertaken in a step 322. After the steps 322, 326, 330 and 332, the program part is terminated and repeated at a given time.

The functional checking can, apart from the illustrated kind on the basis of load values, also be performed on the basis of the setting values. In addition, the monitoring and emergency running measures can be deployed together or separately.

C-LAIMS 1. Control means for an internal combustion engine of a vehicle, comprising first detecting means for providing at least one signal having a value dependent on the setting of a settable device for influencing operation of the engine, second detecting means for providing a signal having a value indicative of engine load but without direct relationship to the setting of the device, and means for carrying out a plausibility check on the basis of the signal values and recognising thm. presence of a fault in or associated wi,th. the detecting means in response to detection of an impermissible 10 difference between the two values or at least two of the values.

2. Control means as claimed in claim 1. wherein the device is settable by electrically actuable setting means operable in dependence on the setting of an element actuable by a driver of the vehicle.

3. Control means as claimed in claim 1 or claim 2, wherein the value of said at least one signal provided by the first detecting means is indicative of the setting of the device and the detection of such an impermissible difference between said two signals is recognised as the presence of a fault in or associated with the first detecting 20 means.

4. Control means as claimed in claim 1, the first detecting means being arranged to provide at least two signals having values dependent on the setting of the device, and means being provided to-carry out a control operation on the basis of at least one of those signal values.

5. Control means as claimed in claim 4, said means for carrying out a control operation being arranged to carry out the operation in the absence of recognition of the presence of such a fault involving the signal values of the first detecting means.

6. Control means as claimed in any one of the preceding claims, comprising means responsive to recognition of the presence of such a fault to form a target value for engine load in dependence on the setting of an element actuable by a driver of the vehicle and to cause the setting of the device to be influenced on the basis of regulation of the value of the signal of the second detecting means towards said target value.

7. Control means as claimed in claim 2, the setting means comprising a stepping drive and the first detecting means comprising a step counter for counting steps of the drive.

8. Control means as claimed in claim 7, comprising means responsive to recognition of the presence of such a fault to cause the counter to be set to a value corresponding to a selected setting of the device when the device is in that setting.

9. Control means as claimed in any one of the preceding claims, wherein the value of the signal provided by the second detecting means is one of induction air mass flow, induction air quantity, induction pressure or basic fuel injection time.

10. Control;beans as claimed in any one of the preceding claims, the means for plausibility checking and fault recognition being arranged to convert the value of the or each signal provided by the first detecting means into an engine load value or to convert the value of the signal provided by the secnnd detecting means into a device setting value, and to compare the converted value with a predetermined tolerance range, the conversion being carried out in dependence on engine speed.

11. Control means as claimed in any one of the preceding claims, the setting device being a throttle flap of the engine.

12. Control means substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.

13. Control means substantially as hereinbefore described with reference to Figs. 1 and 3 of the accompanying drawings.

14. Control means substantially as hereinbefore described with reference to Fig. 4 of the accompanying drawings.

15. An internal combustion engine for a vehicle, the engine being equipped with control means as claimed in any one of the preceding claims.